Barrages

A barrage is a barrier built across a river or estuary, designed to regulate water flow and water level upstream by using gates or sluices. Unlike a conventional dam that primarily stores water, a barrage controls discharge and head to suit varying flow and tidal conditions. Barrages typically span the full river cross-section and consist of multiple movable gates that can be opened or closed as needed.

Barrages serve a range of purposes, including flood control, navigation, water supply, irrigation, and tidal management. By adjusting gate openings, they can maintain a stable upstream water level, ensure sufficient depth for vessels, divert flow into canals, or protect downstream areas from storm surge and flooding. Some barrages are integrated with hydroelectric equipment, using the maintained head across the barrier to drive turbines.

Design and operation involve selecting appropriate gate types (such as sluice gates or radial gates), spillways, and sometimes lock systems for navigation. Gate operations are coordinated to accommodate seasonal rainfall, drought, and tidal cycles. Sedimentation, structural loads, and maintenance access are important considerations in barrage design, as is ensuring reliable operation during flood events.

Notable examples include the Farakka Barrage on the Ganges in India, which manages irrigation and flow to downstream regions, and the Sabarmati Barrage in India, which supplies water to the Sabarmati basin. In the United Kingdom, tidal barrages such as the Thames Barrier are used to protect major urban areas from storm surges and high tides. Barrages remain a distinct class of hydraulic structure aimed at controlling water systems rather than solely storing water.